Expanded clinical and molecular spectrum of guanidinoacetate methyltransferase (GAMT) deficiency

Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine biosynthesis, characterized by excessive amounts of guanidinoacetate in body fluids, deficiency of creatine in the brain, and presence of mutations in the GAMT gene. We present here 8 new patients with GAMT deficiency along with their clinical, biochemical and molecular data. The age at diagnosis of our patients ranges from 0 to 14 years. The age of onset of seizures usually ranges from infancy to 3 years. However, one of our patients developed seizures at age 5; progressing to myoclonic epilepsy at age 8 years and another patient has not developed seizures at age 17 years. Five novel mutations were identified: c.37ins26 (p.G13PfsX38), c.403G>T (p.D135Y), c.507_521dup15 (p.C169_S173dup), c.402C>G (p.Y134X) and c.610_611delAGinsGAA (p.R204EfsX63). Six patients had the c.327G>A (last nucleotide of exon 2) splice-site mutation which suggests that this is one of the most common mutations in the GAMT gene, second only to the known Portuguese founder mutation, c.59G>C (p.W20S). Our data suggests that the clinical presentation can be variable and the diagnosis may be overlooked due to unawareness of this disorder. Therefore, GAMT deficiency should be considered in the differential diagnosis of progressive myoclonic epilepsy as well as in unexplained developmental delay or regression with dystonia, even if the patient has no history of seizures. As more patients are reported, the prevalence of GAMT deficiency will become known and guidelines for prenatal diagnosis, newborn screening, presymptomatic testing and treatment, will need to be formulated.

Statin myotoxicity is associated with changes in the cardiopulmonary function

The mechanism of the muscle toxicity associated with lipid-lowering therapy remains obscure. Pathological and biochemical findings in patients with statin myotoxicity suggest impaired fatty acid oxidation. Exhaled gas analysis can be used to assess substrate utilization including fatty acid oxidation. In order to determine if muscle toxicity due to lipid-lowering therapy might be related to abnormalities in lipid oxidation, exhaled gas analysis was performed in the fasted state on 11 patients subsequent to statin-associated myositis reactions. Results were compared to those of 16 normal controls who were measured both on and off statin therapy. Post-myositis patients showed a depressed anaerobic threshold (AT) (P=0.009) compared to controls while age-adjusted maximal oxygen consumption (VO2max) and ventilatory efficiency (VE/VCO2) were not significantly different. The fasting respiratory exchange ratio (RER) of post-myositis patients off statins was abnormally increased (P=0.00001) as was their S1-slope (P=0.023). Controls demonstrated a significant increase in their RER while taking statins consistent with decreased lipid oxidation (P <0.00001). These findings suggest that abnormal lipid oxidation in certain patients may predispose them to the myotoxicity caused by lipid-lowering therapies.

Unusual brain growth patterns in early life in patients with autistic disorder: an MRI study

OBJECTIVE

To quantify developmental abnormalities in cerebral and cerebellar volume in autism.

METHODS

The authors studied 60 autistic and 52 normal boys (age, 2 to 16 years) using MRI. Thirty autistic boys were diagnosed and scanned when 5 years or older. The other 30 were scanned when 2 through 4 years of age and then diagnosed with autism at least 2.5 years later, at an age when the diagnosis of autism is more reliable.

RESULTS

Neonatal head circumferences from clinical records were available for 14 of 15 autistic 2- to 5-year-olds and, on average, were normal (35.1 +/- 1.3 cm versus clinical norms: 34.6 +/- 1.6 cm), indicative of normal overall brain volume at birth; one measure was above the 95th percentile. By ages 2 to 4 years, 90% of autistic boys had a brain volume larger than normal average, and 37% met criteria for developmental macrencephaly. Autistic 2- to 3-year-olds had more cerebral (18%) and cerebellar (39%) white matter, and more cerebral cortical gray matter (12%) than normal, whereas older autistic children and adolescents did not have such enlarged gray and white matter volumes. In the cerebellum, autistic boys had less gray matter, smaller ratio of gray to white matter, and smaller vermis lobules VI-VII than normal controls.

CONCLUSIONS

Abnormal regulation of brain growth in autism results in early overgrowth followed by abnormally slowed growth. Hyperplasia was present in cerebral gray matter and cerebral and cerebellar white matter in early life in patients with autism.

Nerve conduction changes in patients with mitochondrial diseases treated with dichloroacetate

Serial measurements of nerve conduction velocities and amplitudes were performed in 27 patients with congenital lactic acidemia over 1 year of sodium dichloroacetate (DCA) administration. Patients were treated with oral thiamine (100 mg) and DCA (initial dose of 50 mg/kg) daily. Nerve conduction velocity and response amplitude were measured in the median, radial, tibial, and sural nerves at 0, 3, 6, and 12 months, and plasma DCA pharmacokinetics were measured at 3 and 12 months. Baseline electrophysiologic parameters in this population were generally below normal but as a group were within 2 standard deviations of normal means. Although symptoms of neuropathy were reported by only three patients or their families, nerve conduction declined in 12 patients with normal baseline studies, and worsening of nerve conduction occurred in the two who had abnormalities at baseline. Peripheral neuropathy appears to be a common side effect during chronic DCA treatment, even with coadministration of oral thiamine. Nerve conduction should be monitored during DCA treatment.

A comparison of genetic mitochondrial disease and nucleoside analogue toxicity. Does fetal nucleoside toxicity underlie reports of mitochondrial disease in infants born to women treated for HIV infection?

Recent reports of mitochondrial disease in infants whose mothers were treated in pregnancy with nucleoside analogues are of concern. Chronic nucleoside analogue treatment of adults has long been known to cause mitochondrial DNA depletion with the risk of multisystem disease. Combination nucleoside analogue treatment regimens may have the greatest risk of toxicity. This paper briefly presents the underlying biochemical etiologies and phenotypes of some common genetic mitochondrial diseases in order to provide a comparison with reports of infant toxicity. A standardized method for the diagnosis and evaluation of mitochondrial disease is discussed. A hypothesis, with predictions of the effects of antenatal nucleoside analogue treatment on the fetus, is presented and future directions for research on this problem are suggested.

Autism associated with the mitochondrial DNA G8363A transfer RNA(Lys) mutation

We report a family with a heterogeneous group of neurologic disorders associated with the mitochondrial DNA G8363A transfer ribonucleic acid (RNA)Lys mutation. The phenotype of one child in the family was consistent with autism. During his second year of life, he lost previously acquired language skills and developed marked hyperactivity with toe-walking, abnormal reciprocal social interaction, stereotyped mannerisms, restricted interests, self-injurious behavior, and seizures. Brain magnetic resonance imaging (MRI) and repeated serum lactate studies were normal. His older sister developed signs of Leigh syndrome with progressive ataxia, myoclonus, seizures, and cognitive regression. Her laboratory studies revealed increased MRI T2-weighted signal in the putamen and posterior medulla, elevated lactate in serum and cerebrospinal fluid, and absence of cytochrome c oxidase staining in muscle histochemistry. Molecular analysis in her revealed the G8363A mutation of the mitochondrial transfer RNA(Lys) gene in blood (82% mutant mitochondrial DNA) and muscle (86%). The proportions of mutant mitochondrial DNA from her brother with autism were lower (blood 60%, muscle 61%). It is likely that the origin of his autism phenotype is the pathogenic G8363A mitochondrial DNA mutation. This observation suggests that certain mitochondrial point mutations could be the basis for autism in some individuals.

Kearns-Sayre syndrome presenting as 2-oxoadipic aciduria

A patient with 2-oxoadipic aciduria and 2-aminoadipic aciduria presented at 2 years of age with manifestations typical of organic acidemia, episodes of ketosis and acidosis, progressive to coma. This resolved and the key metabolites disappeared from the urine and blood. At 9 years of age she developed typical Kearns-Sayre syndrome with complete heart block, retinopathy, and ophthalmoplegia. Southern blot revealed a deletion in the mitochondrial genome.

Sensitive assay for mitochondrial DNA polymerase gamma

BACKGROUND

The mitochondrial DNA polymerase gamma is the principal polymerase required for mitochondrial DNA replication. Primary or secondary deficiencies in the activity of DNA polymerase gamma may lead to mitochondrial DNA depletion. We describe a sensitive and robust clinical assay for this enzyme.

METHODS

The assay was performed on mitochondria isolated from skeletal muscle biopsies. High-molecular weight polynucleotide reaction products were captured on ion-exchange paper, examined qualitatively by autoradiography, and quantified by scintillation counting.

RESULTS

Kinetic analysis of DNA polymerase gamma by this method showed a K(m) for dTTP of 1.43 micromol/L and a K(i) for azidothymidine triphosphate of 0.861 micromol/L. The assay was linear from 0.1 to 2 microgram of mitochondrial protein. The detection limit was 30 units (30 fmol dTMP incorporated in 30 min). The linear dynamic range was three orders of magnitude; 30-30 000 units. Imprecision (CV) was 6.4% within day and 12% between days. Application of this assay to a mixed population of 38 patients referred for evaluation of mitochondrial disease revealed a distribution with a range of 0-2506 U/microgram, reflecting extensive biologic variation among patients with neuromuscular disease.

CONCLUSION

This assay provides a useful adjunct to current laboratory methods for the evaluation of patients with suspected mitochondrial DNA depletion syndromes.

Mitochondrial DNA polymerase gamma deficiency and mtDNA depletion in a child with Alpers' syndrome

Deficiency of mitochondrial DNA polymerase gamma activity was found in a patient with mtDNA depletion and Alpers' syndrome. Metabolic evaluation revealed fasting hypoglycemia, dicarboxylic aciduria, and reduced activity of the electron transport chain in skeletal muscle. The patient died in early childhood of fulminant hepatic failure, refractory epilepsy, lactic acidemia, and coma. mtDNA content was 30% of normal in skeletal muscle and 25% in the liver. The activity of mtDNA polymerase gamma was undetectable.

A possible role of coenzyme Q10 in the etiology and treatment of Parkinson's disease

Parkinson's disease (PD) is a degenerative neurological disorder. Recent studies have demonstrated reduced activity of complex I of the electron transport chain in brain and platelets from patients with PD. Platelet mitochondria from parkinsonian patients were found to have lower levels of coenzyme Q10 (CoQ10) than mitochondria from age/sex-matched controls. There was a strong correlation between the levels of CoQ10 and the activities of complexes I and II/III. Oral CoQ10 was found to protect the nigrostriatal dopaminergic system in one-year-old mice treated with MPTP, a toxin injurious to the nigrostriatal dopaminergic system. We further found that oral CoQ10 was well absorbed in parkinsonian patients and caused a trend toward increased complex I activity. These data suggest that CoQ10 may play a role in cellular dysfunction found in PD and may be a potential protective agent for parkinsonian patients.

Analysis of organic acids, amino acids, and carnitine in dogs with lipid storage myopathy

Abnormal accumulations of lipid droplets, localized predominantly in histochemical type 1 fibers, were observed in fresh frozen sections of muscle biopsies from 25 dogs with myalgia, weakness, and muscle atrophy. Compared to controls, lactic acidemia, hyperalaninemia, lactic and pyruvic aciduria, variably increased urinary excretion of carnitine esters, and muscle carnitine deficiency were present. These findings support a metabolic block in oxidative metabolism resulting in lactic acidemia in dogs with lipid storage myopathy.

Absorption, tolerability, and effects on mitochondrial activity of oral coenzyme Q10 in parkinsonian patients

We report a pilot study of three oral doses of coenzyme Q10 (CoQ10) (200 mg administered two, three, or four times per day for 1 month) in 15 subjects with Parkinson's disease. Oral CoQ10 caused a substantial increase in the plasma CoQ10 level. It was well tolerated, but at the highest dose (200 mg four times per day) mild, transient changes in the urine were noted. CoQ10 did not change the mean score on the motor portion of the Unified Parkinson's Disease Rating Scale. There was a trend toward an increase in complex I activity in the subjects.

Osteopenia in Rett syndrome

Bone density analysis, dietary intake, and anthropometrics were compared in 20 subjects with Rett syndrome (RS), 25 normal control subjects, and 11 girls with cerebral palsy. Bone mineral density, bone mineral content, and spine (bone) mineral density were significantly reduced in the RS group. When weight and age were kept constant, the bone density was still reduced in the patients with RS. Subjects with RS are at risk for osteoporosis.

Diabetes and mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS): radiolabeled polymerase chain reaction is necessary for accurate detection of low percentages of mutation

A 6-yr-old boy presented with muscle weakness, lactic acidemia, and insulin-dependent diabetes mellitus (IDDM). Using PCR and restriction enzyme analysis, he was found to have the classical A3248G mitochondrial DNA (mtDNA) mutation frequently associated with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS). The mutation was confirmed by sequencing muscle mtDNA. The mutation in mtDNA from muscle, lymphoblasts, and blood was clearly demonstrable by standard methods using ethidium bromide staining. His mother also had IDDM, but no A3243G mutation could be detected in her blood or transformed lymphoblasts using the same PCR technique. When PCR was carried out in the presence of [32P]deoxycytidine triphosphate, subsequent autoradiography detected the presence of the mutation at low levels in mtDNA from the mother's lymphoblasts and blood. Study of the mother's muscle showed a mitochondrial myopathy, despite the fact that she was asymptomatic. We emphasize that the increased sensitivity of radiolabeled PCR may be necessary to detect small percentages of heteroplasmic A3243G mtDNA mutation in blood from diabetic subjects. Otherwise the incidence of mtDNA mutations in both IDDM and non-insulin dependent diabetes may be underestimated.

Coenzyme Q10 levels correlate with the activities of complexes I and II/III in mitochondria from parkinsonian and nonparkinsonian subjects

The activities of complex I and complex II/III in platelet mitochondria are reduced in patients with early, untreated Parkinson's disease. Coenzyme Q10 is the electron acceptor for complex I and complex II. We found that the level of coenzyme Q10 was significantly lower in mitochondria from parkinsonian patients than in mitochondria from age- and sex-matched control subjects and that the levels of coenzyme Q10 and the activities of complex I and complex II/III were significantly correlated.

Neurologic abnormalities in infantile autism

Neuroanatomic, pathologic, and neurobehavioral studies point to a cerebellar and parietal abnormality in autism. We used a standardized protocol to examine neurologic function in 28 pediatric autistic subjects and 24 pediatric normal healthy volunteer controls. As a group, the autistic subjects had quantitative measures from magnetic resonance imaging suggesting hypoplasia or hyperplasia of the cerebellar vermis, as well as measurements of posterior corpus callosum suggesting abnormalities of posterior cortex. In groups of tests that reflect cerebellar and parietal function, the neurologic abnormalities detectable by clinical examination were significantly greater for autistic subjects than for normal controls. These studies confirm that the structural and behavioral deficit in autism does lead to abnormalities that can be detected on the clinical neurologic examination.

Leber's hereditary optic neuropathy plus dystonia is caused by a mitochondrial DNA point mutation

A novel point mutation in the ND6 subunit of complex I at position 14,459 of the mitochondrial DNA (MTND6*LDY T14459A) was identified as a candidate mutation for the highly tissue-specific disease. Leber's hereditary optic neuropathy plus dystonia. Since the MTND6*LDYT14459A mutation was identified in a single family, other pedigrees with the mutation are needed to confirm its association with the disease. Clinical, biochemical, and genetic characterization is reported in two additional pedigrees. Leber's hereditary optic neuropathy developed in two family members in one pedigree. The daughter had clinically silent basal ganglia lesions. In a second pedigree, a single individual presented with childhood-onset generalized dystonia and bilateral basal ganglia lesions. Patient groups that included individuals with Leigh's disease, dystonia plus complex neurodegeneration, and Leber's hereditary optic neuropathy did not harbor the MTND6*LDYT14459A mutation, suggesting that this mutation displays a high degree of tissue specificity, thus producing a narrow phenotypic range. These results confirm the association of the MTND6*LDYT14459A mutation with Leber's hereditary optic neuropathy and/or dystonia. As the first genetic abnormality that has been identified to cause generalized dystonia, this mutation suggests that nuclear DNA or mitochondrial DNA mutations in oxidative phosphorylation genes are important considerations in the pathogenesis of dystonia.

Neuropharmacology of progressive myoclonus epilepsy: response to 5-hydroxy-L-tryptophan

Low concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid (CSF) of patients with progressive myoclonus epilepsy (PME) suggest hypofunctional serotonergic neurotransmission. To study this hypothesis, we enrolled 6 patients with PME [Unverricht-Lündborg disease (U-L), mitochondrial encephalomyopathy, or Lafora disease] in a controlled, double-blinded, dose-ranging, cross-over add-on pilot clinical trial of 5-hydroxy-L-tryptophan (L-5-HTP) plus carbidopa after 2 other patients had received open-label L-5-HTP for compassionate use. Prestudy CSF 5-HIAA concentrations were low (< 20 ng/ml) in 6 patients regardless of the etiology of PME. One patient with U-L disease showed clinical improvement and a fivefold increase in CSF 5-HIAA, and 1 with Lafora disease showed a twofold increase in CSF 5-HIAA without improvement. A patient with Lafora disease reported enough improvement in myoclonus-evoked convulsions to continue chronic use of the drug. One patient with mitochondrial encephalomyopathy developed status epilepticus during treatment with L-5-HTP. As a group, patients had no statistically significant changes in myoclonus evaluation scale scores, subjective and objective measures of ataxia, seizure frequency, antiepileptic drug (AED) levels, or routine blood tests. These data suggest a serotonergic abnormality regardless of the underlying etiology of PME, but one that seldom responds to acute treatment with L-5-HTP.

Low platelet mitochondrial complex I and complex II/III activity in early untreated Parkinson's disease

Following the discovery of inhibition of electron transport complex 1 by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which produces a parkinsonian syndrome in humans, monkeys, and mice, several laboratories have reported abnormalities of complex I and other electron transport complexes (ETCs) in various tissues from patients with Parkinson's disease (PD). Criticism of the significance of these findings in the etiology of PD has centered on whether drug treatments or the debilitation of the disease process itself produced the low ETC activities. We present results from a blinded study of platelet mitochondrial ETC activities in 18 early untreated PD patients and 18 age- and sex-matched controls and in 13 spousal controls. Lower complex I activity in platelet mitochondria of PD patients was seen in early untreated disease and thus cannot be due to debilitation or drug therapy. Home environmental factors seem an unlikely explanation for the reduced complex I activity in PD patients but have not been excluded. Complex II/III activity was also reduced by 20% in PD compared with age-/sex-matched controls. The low complex I and II/III activities in platelet mitochondria appear to be related to the etiology of PD.

Oxidative metabolism in Rett syndrome: 1. Clinical studies

The etiology of Rett syndrome (RS) remains a mystery. The clinical phenotype has similarities to that of patients with mitochondrial defects of oxidative metabolism. There is evidence of lactate and pyruvate elevations in blood and CSF in some patients. Over the last 10 years we have studied girls with RS looking for evidence of a defect in oxidative metabolism. We present data on lactate and pyruvate blood measurements in 30 patients with RS with repeated measurements performed over time in many. Taken as a whole the means of measurements of lactate and pyruvate fall within the control range, however, individual patients have marked elevation of both lactate and pyruvate with considerable fluctuation over time. Nine girls with typical RS were studied in detail using a clinical protocol designed to identify disorders of oxidative metabolism. These patients underwent fasting for 24 hours, glucose loading and alanine loading tests. Seven girls had skin and muscle biopsies performed. One patient admitted with particularly high blood lactate levels underwent hourly blood collections over a 24 hour period during which state of alertness was noted and respiratory monitoring was performed. In this patient serial blood sampling for lactate performed. In this patient serial blood sampling for lactate performed with oxypneumocardiogram recording demonstrated a fall in plasma lactate to normal levels during sleep when the respiratory pattern was normal. Such fluctuations of plasma lactate apparently correlated with sleep/wake state and respiration suggest that in some patients with RS lactate elevations may arise from respiratory abnormalities. Other positive findings included prediabetic glucose responses in three girls. Ammonia levels following alanine loading were normal in all patients.

Oxidative metabolism in Rett syndrome: 2. Biochemical and molecular studies

In an attempt to identify a possible defect of mitochondrial metabolism in Rett syndrome we studied 9 girls with typical Rett syndrome using a clinical protocol designed to identify disorders of oxidative metabolism. One girl, (RO) had marked lactic acidemia. Biochemical studies on samples from these patients included leukocyte pyruvate carboxylase assay, serum biotinidase and skin fibroblast pyruvate production, pyruvate dehydrogenase, citrate synthetase and 2-oxoglutarate dehydrogenase assay. Muscle electron transport activities were studied on samples from 4 typical Rett patients including RO. Mitochondrial DNA (mtDNA) mutational analysis for the np3243 MELAS mutation, the np8993 NARP mutation, the np8344 MERFF mutation and the 4977 kb common deletion found in Kearns-Sayre syndrome and aged tissues were tested for in 1 of the muscle samples and 2 blood samples from typical Rett patients. Western blotting of electron transport complex III was performed on mitochondrial samples obtained from autopsy brain tissue in 2 Rett patients and compared to pediatric control brain samples. No abnormalities were found in blood biotinidase or pyruvate carboxylase. Western blotting of 2 Rett brain mitochondrial samples for complex III appear normal. Pyruvate consumption in medium from 8 Rett fibroblast lines grown with and without dichloroacetate (DCA) showed a normal fall in pyruvate suggesting normal pyruvate dehydrogenase activity in these cells, however the fibroblasts from patient RO had a high pyruvate production in culture. Pyruvate dehydrogenase, 2-oxo-glutarate dehydrogenase and citrate synthetase activities in 8 Rett fibroblast lines were normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Impairment in shifting attention in autistic and cerebellar patients

MRI and autopsy evidence of early maldevelopment of cerebellar vermis and hemispheres in autism raise the question of how cerebellar maldevelopment contributes to the cognitive and social deficits characteristic of autism. Compared with normal controls, autistic patients and patients with acquired cerebellar lesions were similarly impaired in a task requiring rapid and accurate shifts of attention between auditory and visual stimuli. Neurophysiologic and behavioral evidence rules out motor dysfunction as the cause of this deficit. These findings are consistent with the proposal that in autism cerebellar maldevelopment may contribute to an inability to execute rapid attention shifts, which in turn undermines social and cognitive development, and also with the proposal that the human cerebellum is involved in the coordination of rapid attention shifts in a fashion analogous to its role in the coordination of movement.

Carbidopa/levodopa and selegiline do not affect platelet mitochondrial function in early parkinsonism

Previous studies have demonstrated impaired complex I activity in platelets from Parkinson's disease (PD) patients who were receiving levodopa and other medications for their disease. Eleven patients with early PD underwent three sequential plateletphereses: while on no medication, after receiving carbidopa/levodopa for 1 month, and after receiving carbidopa/levodopa plus selegiline for 1 additional month. As expected, carbidopa/levodopa and selegiline significantly improved motor function in these patients. Treatment with carbidopa/levodopa alone and carbidopa/levodopa plus selegiline did not affect the activities of complexes I, II/III, and IV and citrate synthetase. These observations support the hypothesis that impaired complex I activity in PD patients is a characteristic of the disease and not due to medications.

Acute basal ganglia infarction in propionic acidemia

An 8-year-old girl with propionic acidemia had acute and rapidly fatal symmetric necrosis of the caudate, globus pallidus, and putamen. Clinical presentation was with acute aphasia, generalized hypotonia, and muscle weakness. There was no evidence of metabolic decompensation, and analysis of the organic acids of the urine indicated good metabolic control. Organic acids in the cerebrospinal fluid were unremarkable. These observations indicate that the pathophysiology of "metabolic stroke" is more complicated than previously thought.

Neuropathology of propionic acidemia: a report of two patients with basal ganglia lesions

Propionic acidemia is a rare genetic disorder of amino acid metabolism caused by deficient activity of propionyl coenzyme A carboxylase. Neuropathologic changes previously reported in infants have been white-matter vacuolization or spongiosis. In children who survive beyond infancy, abnormalities have been found primarily in the basal ganglia. We report neuropathologic findings in two patients with propionic acidemia diagnosed in infancy who survived 35 months and 9 years, respectively. Examination of the brain of the 35-month-old boy showed vascular and parenchymal mineralization, focal pallor and spongy change, and foci of acute neuronal injury. These changes were similar to those previously described. The 9-year-old girl was in good metabolic control when she died, and presented a neuropathologic picture not previously described. She was found at autopsy to have acute hemorrhagic lesions in the caudate, putamen, and globus pallidus bilaterally and in the left ventral thalamus. There was focal neuronal loss, but no acute hypoxic/ischemic neuronal injury. Vascular proliferation and swollen endothelial cells were seen in the basal ganglia, thalamus, and substantia nigra, but not in other regions of the brain. Electron microscopy showed swelling of endothelial cells with viable adjacent brain parenchyma. The endothelial changes suggest a breakdown of the blood-brain barrier.

Impairment in shifting attention in autistic and cerebellar patients

MRI and autopsy evidence of early maldevelopment of cerebellar vermis and hemispheres in autism raise the question of how cerebellar maldevelopment contributes to the cognitive and social deficits characteristic of autism. Compared with normal controls, autistic patients and patients with acquired cerebellar lesions were similarly impaired in a task requiring rapid and accurate shifts of attention between auditory and visual stimuli. Neurophysiologic and behavioral evidence rules out motor dysfunction as the cause of this deficit. These findings are consistent with the proposal that in autism cerebellar maldevelopment may contribute to an inability to execute rapid attention shifts, which in turn undermines social and cognitive development, and also with the proposal that the human cerebellum is involved in the coordination of rapid attention shifts in a fashion analogous to its role in the coordination of movement.

Abnormality of cerebellar vermian lobules VI and VII in patients with infantile autism: identification of hypoplastic and hyperplastic subgroups with MR imaging

OBJECTIVE

Infantile autism is a neurobehavioral disorder that is widely believed to have etiologically distinct subtypes, including subtypes with a genetic basis, but no neuroanatomic evidence firmly supports this belief. To date, only one type of cerebellar abnormality has been identified in patients with autism: hypoplasia of the vermis and hemispheres. By using a large sample of autistic patients and healthy volunteers along with precise MR imaging and quantitative procedures, we sought to replicate previous reports of cerebellar vermian hypoplasia in autism and to identify additional subtypes of cerebellar abnormality.

MATERIALS AND METHODS

Using MR technology, we imaged and measured posterior and anterior vermian regions in 50 autistic patients (2-40 years old) and 53 healthy control subjects (3-37 years old). The autistic patients had social, language, cognitive, behavioral, and medical history characteristics that were typical of the general autistic population. By using precise procedures for positioning and aligning MR slices, we obtained comparable MR images within and across subject groups.

RESULTS

Statistical analyses showed two subgroups of autistic patients, one (86% of the patients) with findings consistent with vermian hypoplasia and another (12% of the patients) with evidence of vermian hyperplasia. The hypoplasia subgroup included 43 patients whose mean midsagittal area for vermian lobules VI and VII was 237 +/- 38 mm2, and the hyperplasia subgroup included six patients whose mean area was 377 +/- 12 mm2. Thus, the area of lobules VI and VII in the hypoplasia subgroup was 16% smaller than the mean area in the control subjects (282 +/- 42 mm2) (p < .0001), whereas that in the hyperplasia subgroup was 34% larger (p < .0001). Analyses showed that these two subtypes of vermian abnormalities were present across all ages of autistic patients studied.

CONCLUSION

Two different subtypes of autistic patients can be identified on the basis of the presence of vermian hypoplasia or hyperplasia as seen on MR images. Possible origins for vermian hypoplasia include environmental trauma and genetic factors.

Cerebellar and cerebral abnormalities in Rett syndrome: a quantitative MR analysis

Rett syndrome is a neurodegenerative disease of young girls that begins in early childhood with autismlike behavior and loss of language skills, and progresses with marked deterioration of the motor system in the second decade of life. The purpose of this study was to determine if neuroanatomic changes detected with MR imaging could help to explain the clinical presentation and progression of signs and symptoms in these patients. Accordingly, computer-assisted planimetry was used to measure various dimensions of cerebral, cerebellar, and brainstem structures on sagittal and transverse MR images of 13 patients with Rett syndrome and 10 healthy volunteers. Dimensions of the cerebrum, basal ganglia, cerebellum, and brainstem were measured on transverse images. Areas of cerebellar vermian lobules, the fourth ventricle, the pituitary gland, and the corpus callosum were measured on sagittal images. Fourteen dimensions and areas were measured in each patient and each control subject; according to two-tailed Student's t tests, all but two values were significantly smaller in the patients with Rett syndrome than in control subjects. Graphing the measurements against age by using simple linear regression revealed progressive cerebellar atrophy without evidence of atrophy of the brainstem or cerebrum. Our results indicate that patients with Rett syndrome have global hypoplasia of the brain and progressive cerebellar atrophy increasing with age. Cerebellar atrophy with age may contribute to the deterioration of the motor system seen in older patients with Rett syndrome.

Cardiac function, substrate utilization, and myocardial energy metabolism studied with 31-P NMR spectroscopy during acute hypoglycemia and hyperketonemia

Whether severe hypoglycemia alone or in combination with hyperketonemia might cause deterioration of cardiac function has been controversial. Therefore, the influence of acute hypoglycemia (mean 33 mg/dL) with and without hyperketonemia (mean 1.3 and 3.3 mM) on cardiac function, substrate utilization, and myocardial high energy phosphate levels was studied in 10 mongrel dogs. After 45 min of hypoglycemia, mean aortic pressure, total peripheral resistance, and myocardial oxygen consumption had increased significantly, but other hemodynamic parameters and regional myocardial function had not changed. Additional infusion of 3-hydroxybutyrate did not affect hemodynamic variables significantly. During both metabolic interventions in vivo phosphorus-31 nuclear magnetic resonance spectroscopy showed stable levels of myocardial phosphocreatinine, ATP, as well as the phosphocreatinine/ATP (3.0-3.2) ratio. Biochemical measurements revealed that hyperketonemia led to significant alterations in arterial concentrations and arteriocoronary venous differences of selected citric acid cycle intermediates, thus confirming previous reports which suggested a blockade of the 2-oxoglutarate-dehydrogenase reaction induced by ketone body oxidation. However, despite this blockade, the energy supply to the heart was not impaired as shown by normal nuclear magnetic resonance spectroscopy and cardiac performance. It is speculated, that the blockade might be due to an enhanced NADH/NAD ratio.

Ketone bodies maintain normal cardiac function and myocardial high energy phosphates during insulin-induced hypoglycemia in vivo

It has been suggested that myocardial utilization of ketone bodies might cause deterioration of cardiac function. Therefore, the influence of ketonemia (mean: 1.3 and 3.3 mM) in the presence of hypoglycemia (mean: 33 mg/dl) on cardiac function, substrate utilization and myocardial high energy phosphate levels was studied in 10 mongrel dogs. Hypoglycemia alone led to a significant increase of mean aortic pressure, total peripheral resistance and myocardial oxygen consumption, but other hemodynamic parameters and regional myocardial function were not changed. Additional infusion of 3-hydroxybutyrate did not affect hemodynamic variables significantly. During both metabolic interventions in vivo phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy showed stable levels of myocardial Pi, PCr, ATP, as well as PCr/Pi (3.2-3.4) and PCr/ATP (3.0-3.2) ratios. Biochemical measurements revealed that ketonemia led to significant alterations in arterial concentrations and arterio-coronary venous differences of selected citric acid cycle intermediates, thus confirming previous reports which suggested a blockade of the 2-oxoglutarate-dehydrogenase reaction induced by ketone body oxidation. However, despite this blockade, the energy supply to the heart was not impaired as shown by normal NMR spectroscopy and cardiac performance. It is speculated that the blockade might be due to an enhanced NADH/NAD ratio.

Abnormalities of the brain in nonketotic hyperglycinemia: MR manifestations

MR imaging in seven patients (4 days to 38 months old) with nonketotic hyperglycinemia showed age-related findings of progressive atrophy and delayed myelination. Parenchymal volume loss was found as early as 4 days after birth and increased in severity with increasing age to 27 months. Both supratentorial and infratentorial volume loss were present in the most severely affected patients. The corpus callosum was abnormally thin in all patients. The state of myelination of the CNS was assessed on T2-weighted images. Decreased or absent myelination within supratentorial white-matter tracts was detected in all four patients 10 months of age or older. Myelination of the brainstem and cerebellum progressed normally. No correlation was found between the degree of volume loss or abnormality of myelination demonstrated by MR and the concentration of glycine in the CSF or plasma. Abnormalities shown by MR correlate well with known pathologic findings in patients with nonketotic hyperglycinemia.

High-performance liquid chromatographic measurement of selected blood citric acid cycle intermediates

We describe a high-performance liquid chromatographic (HPLC) method for analysis of the intermediates of the citric acid cycle. Using two Aminex HPX-87H columns in series at 36 degrees C, the early eluting compounds cis-aconitate, oxaloacetate, alpha-ketoglutarate and citrate-isocitrate can be resolved. Acetonitrile is used for extraction of citric acid cycle intermediates from blood as interfering ultraviolet absorbing peaks are present with perchloric acid or trichloroacetic acid extraction. Acetonitrile extraction is compared with perchloric acid extraction of citric acid cycle intermediates from plasma. Low recovery of some organic acids from blood seems not to be due to enzymatic degradation. Storage of acetonitrile extracts in liquid nitrogen led to a small but significant decrease in pyruvate levels in human blood. However, significant changes in other organic acids were not seen. HPLC methodology allows study of the citric acid cycle in tissue samples as well as blood and promises to facilitate the investigation of human disorders of energy metabolism.

Pyruvate dehydrogenase activity in osmotically shocked rat brain mitochondria: stimulation by oxaloacetate

Pyruvate dehydrogenase complex activity (PDHC) measured by CO2 release isotopic assay has generally been much lower than activity measured by the spectrophotometric arylamine acetyltransferase assay (ArAT). Decarboxylation of [1-14C]pyruvate was measured in osmotically shocked rat brain cortical mitochondria. Activity is dependent on the concentration of the substrate pyruvate. Activity of 74.6 units +/- 12.3 SD (n = 22) was observed at 4 mM pyruvate (1 unit = 1 nmol pyruvate decarboxylated/min/mg protein). Activity was dependent on added NAD, CoA, and thiamine pyrophosphate, implying increased mitochondrial permeability after osmotic shock. Freeze/thaw with sonication of the mitochondrial preparation reduced PDHC activity to 11.5 units +/- 3.0 SD (n = 4). Oxaloacetate produced a marked stimulation of activity. The optimal assay contained 3 mM oxaloacetate, and without oxaloacetate activity fell to 15.4 units +/- 9.9 SD (n = 8). These studies highlight the importance of optimal substrate concentrations in the CO2 release isotopic PDHC method. Higher PDHC activity is found with intact mitochondria and thus activity values should be interpreted in the light of the presence or absence of intact mitochondria in individual preparations.

The orthopedic management of Rett syndrome

Musculoskeletal deformity sufficiently severe to require orthopedic surgery is a significant problem in Rett syndrome. Preliminary results from the study of 16 patients suggest deformity in nearly all patients. Eight patients in stage III and seven patients in stage IV showed clinical evidence of scoliosis. Radiographic studies confirmed a structural curve in nine of ten patients studied. Heel cord tightening was seen in nine of 16 patients. Hip instability was identified as an area of potential concern in the Rett patient.

Peripheral nerve findings in Rett syndrome

Sural nerve and peroneus brevis muscle biopsies were studied in 12 patients with Rett syndrome, ten with the typical form of the disorder according to 1985 criteria, and two with atypical features. Ages ranged from 23 months to 25 years. All stages of the disease were represented. There was evidence of a mild axonal neuropathy in seven of 12 patients. Degenerative and occasional regenerative changes were seen in five sural nerve biopsies, including one from the youngest patient in the series, who was normally nourished and fully ambulatory. Occasional nonspecific ultrastructural abnormalities were present, including accumulation of pi granules in Schwann cells and Hirano bodies within axons. However, morphometric analysis of the four nerves in which these alterations were most prominent showed a normal density and size distribution of myelinated fibers. Enzyme histochemistry of the peroneus brevis biopsies demonstrated abnormal predominance of type II muscle fibers in three of the 12 biopsies and atrophy of type I fibers in one patient.

The nutritional aspects of Rett syndrome

Nutrition is a major problem for the Rett patient. We have studied 21 girls with Rett syndrome (19 typical, two atypical). We report our experience in this population with the nutritional aspects of Rett syndrome, the typical dietary habits, and various nutritional deficiencies. Further experience with the use of high fat diets is reported.

Cognitive profile of Rett syndrome

We report preliminary studies in 18 girls with Rett syndrome (15 typical, three atypical cases) who were studied using a number of neuropsychologic measures. Results indicate a relative preservation of gross motor and daily living skills at the developmental level of the age of onset of the condition. Other adaptive functions were more depressed. Higher levels of object permanency were found in this population than reported previously. Our results indicate that islands of motor and intellectual function persist in Rett syndrome patients. These data may be useful for therapeutic intervention.

The history and challenge of Rett syndrome

Rett syndrome was first described in 1966 by Dr Andreas Rett, who reported in German his findings in 22 patients. Recognition of the syndrome grew slowly until 1983, when a series of 35 patients from several countries was reported in English. By 1987, the number of known cases had grown to over 1,250 worldwide, the International Rett Syndrome Association had been founded, and international conferences on the syndrome were being held regularly. Although a developmental staging system has been devised, many questions remain concerning the course of the disease. Rett syndrome poses a challenge to the physicians, therapists, psychologists, educators, and families involved with affected patients, as well as to researchers investigating the syndrome.

Recommendations regarding handling of the necropsy in Rett syndrome

In order to maximize biochemical, neurochemical, molecular, and pathologic information from patients with Rett syndrome, a uniform procedure has been developed for the conduct of the postmortem examination. Tissue should be prepared for freezing, for electron microscopy studies, and for standard histologic examination. For the purposes of uniformity, three central repositories for necropsy materials have been established and are available at all times. In the event of the death of a patient with Rett syndrome, parents who consent to necropsy should request that materials be handled according to the protocol and transported under appropriate conditions to the central repository. The National Neurological Research Bank (Los Angeles), the Brain Tissue Bank (Belmont, Mass), and the Department of Neuropathology at Johns Hopkins Hospital (Baltimore) have agreed to serve as repositories for tissues. A committee of the International Rett Syndrome Association medical advisory panel will monitor this process in cooperation with the directors of the respective tissue banks.

Electroencephalographic abnormalities in Rett syndrome

Electroencephalograms were performed on 11 girls with Rett syndrome between the ages of 4 and 14 years. Electroencephalographic abnormalities included slowing and disorganization of background activity while awake, multifocal epileptiform discharges maximal over the central and temporal regions, and intermittent, high-amplitude discharges followed by relative attenuation of background activity during sleep. Electroencephalographic patterns were remarkably similar in all patients and may be of diagnostic assistance in suspected cases.

Interferon alfa-2b in the treatment of chronic granulocytic leukemia

Studies of the effect of interferon on the growth of colonies of myeloid leukemic blasts, myeloma colony-forming cells and normal hemopoietic precursor cells have shown that interferon does not specifically inhibit the growth of the malignant cells in culture, i.e. the growth of the malignant and the normal precursor cells are inhibited equally. However, interferon markedly reduces the self-renewal capacity of acute myeloid leukemic blasts and myeloma cells. This observation suggested that interferon should be tested for its ability to prolong remissions rather than as a remission-inducing agent. We have tested the ability of interferon alfa-2b (Intron A; Schering-Plough) to prolong remissions induced by busulfan in patients with chronic granulocytic leukemia (CGL). The leukocyte doubling time (Td) and remission duration on no therapy was compared to the values observed during interferon alfa-2b maintenance therapy. Fourteen patients have been started on study and seven have received interferon alfa-2b for three months or more. All seven have shown slowing of the leukocyte Td and prolongation of the remission duration after interferon alfa-2b therapy. A larger study, with longer follow-up, will be required to determine whether interferon alfa-2b therapy will slow or prevent progression of CGL to the blast phase and prolong survival.

Interferon alfa-2b in the treatment of chronic granulocytic leukemia

Studies of the effect of interferon on the growth of colonies of myeloid leukemic blast cells, myeloma colony-forming cells, and normal hemopoietic precursor cells have demonstrated that interferon shows no specificity in inhibiting the growth of these cells in culture (ie, growth of the malignant and normal precursor cells is equally inhibited). However, interferon markedly reduces the self-renewal capacity of acute myeloid leukemic blast cells and myeloma cells. This observation suggested that interferon's ability to prolong rather than induce remissions should be tested. We have studied the ability of interferon alfa-2b (Intron A) to prolong remissions induced by busulfan (Myleran) in patients with chronic granulocytic leukemia (CGL). The leukocyte doubling time and remission duration among patients receiving no therapy was compared with the values observed during interferon alfa-2b maintenance therapy. Nine patients have begun the study; five have completed 3 months of interferon alfa-2b therapy. In four (80%) of the five patients, there has been a significant slowing of the leukocyte doubling time and prolongation of the remission duration. A larger study, with longer follow-up, will be required to determine whether interferon alfa-2b therapy will slow progression of CGL to the blast phase and prolong survival.

Therapeutic effects of a ketogenic diet in Rett syndrome

Seven girls (age 5 to 10 years) with Rett syndrome were investigated extensively. In 6 patients elevations of blood pyruvate were found. Blood lactate levels were marginally elevated. Two patients had variably elevated blood glucose levels. Metabolic studies were otherwise normal apart from minimally elevated blood ammonia levels in 3 of 5 patients tested, 2 of whom were on valproic acid. All 7 patients had anticonvulsant resistant seizures. EEG changes included generalized slowing and multifocal spike wave discharges, and pseudo-periodic burst-suppression patterns during sleep. Respiratory monitoring revealed apneic episodes only during the waking record. Six patients were below the 5th centile for weight despite normal caloric intake. Treatment with ketogenic diets, using medium chain triglyceride (MCT) oil when possible, has improved seizure control in the 5 patients who could tolerate the diet. Slight behavioral and motor improvement has occurred in these 5 patients and 6 of 7 patients on high fat diets have gained weight. With a possible defect in carbohydrate metabolism and a difficult seizure disorder, use of a ketogenic diet is logical and appears to produce clinical benefit in patients with Rett Syndrome.

A microchamber for polarographic assay

A glass micro-chamber which allows polarographic assay in a volume of 180 microliter is described. The conical shape of this chamber allows efficient mixing with a Teflon magnetic flea. This chamber facilitates the study of the small quantities of mitochondria obtained from human tissue biopsies or animal sources. The polarographic assay of mouse liver mitochondria is described.

C-reactive protein in childhood dermatomyositis

Serum levels of C-reactive protein (CRP) were determined in 9 patients with childhood dermatomyositis. Four children were seen during clinical relapse and all had serum CRP levels less than 1 mg/l. In addition direct immunofluorescent staining of muscle biopsies from 4 patients showed no evidence of CRP deposition in muscle tissue. Such patients appear to be able to produce CRP in response to acute infections, and it is suggested therefore that the pathological process in childhood dermatomyositis may not induce a significant CRP response.